Telephony.



No. 688,293. Patented Decylo, |901. G. A. cAnnwELL.

` i INVENTOB l Bvw W- nw' HISATTORNEY UNITED STATES PATENT OEEIcE.

GEORGE A. OARDWELL, OF NEW YORK, N. Y.

TELEPHONY.

SPECIFICATION forming part of Lettere Patent No. 688,293, dated December 1o, 1901. Application iiled November 16, 1899. Renewed May 10, 1901. Serial N0. 59,681. (No model.)

To @ZZ whom, it may concern.'

Be it known that I, GEORGE ALEXANDER OARDWELL, of the city, county, and State of New York, have invented a new and useful Improvement in the Art of Telephony, of which the following is a specification.

The object of my invention is to reinforce the magnetic eifect of a main-line telephonecurrent. This is accomplished by causing electrical pulsations from a local battery of the same kind and having the -same characteristics as the pulsations of the main line to influence the main-line magnet. The variations of pressure between the electrodes of a microphone in the main circuit are utilized to cause these corresponding pulsations in the auxiliary or local circuit.

The drawing accompanying myapplication and forming a part of the specification illustrates diagrammatically a'system embodying my improvement, and it is to be distinctly understood that the principle underlying my improvement may be employed in a variety of ways.

. In the drawing, D designates a permanent magnet. Around the polarextension e of this magnet are placed two separate vcoils A and C', and around polar extension e2 are placed two separate coils A" C", these four coils having the same resistance.

d designates the main-line circuit, which traverses coils C O" and passes out to ground or to a metallic connection. Placed between the polar extensions e e2 is a fork F, rigidly supported atf, so as to have a definite normal position, with its tines disposed at equal distances in front of the said extensions. The fork Fis made of soft iron.

h, 7L', h2, and lt3 are arms or supports arranged in pairs, the members of each pair being insulated from each other, as shown at t' t'.

The arms h and h are secured to one tine of the fork E by means of insulating-bushing 7.a, and the arms h2 and h3 are secured to the other tine by means of an insulating-bushing 7c'. To the arms h and h', respectively, are secured carbon disks m and fm', and to the arms h2 and h3, respectively, are attached carbon disks fm2 and m3, the whole constituting a part of a microphone system, the disks m and m' being in contact, respectively, with the disks m2 and m3.

their arms h and h2, are included in the circ cuit 1' of a local batteryn. circuit are connected to the primary of an induction-coil R, the secondary of which coil is included within a local or trunk line S, which Vincludes a receiver s. Y

The method of reinforcing the magnetic effect of the main-line current is as follows: Pulsations of current from the main line d in the magnet-coils C O" cause the vibration of the two arms of the fork F in equal and opposite directions, thereby varying the pressure between the microphonic disks m and m3 and'm and fm2. The local circuit from the battery p passing through the disks m' m3 is caused to pulsate in unison with'the pulsations ofthe main line,thereby causing similarl pulsations in the circuit 0,Which traverses the coils A A", producing'a magnetic edect upon the coilse e2, which reinforces the magnetic effect of the pulsations in the mainline. The local or outgoing circuit from the battery vn passes through the disks m m2 and its current is caused to pulsate by the varying pressure between said disks and in Vunison with the'pulsations in the main line. Through the induction-coil R this current will cause similar pulsations in the outgoing line S, which vline includes the receiver s.

From the above it Will be seen that the essence of my invention is the reinforcement of the weak magnetic elfect ofthe current from the main line by a current'from a local'battery having pulsations ofthe same kind as the pulsations of the main line, the current from the local battery beingcaused to influence the same magnet as the current from the main line. By reason of the instantaneous character of the induced current from the coil P there is no retardation and no confusion of sound at the receiver.

While I have referred to the circuit d as the main line, it will of course be readily understood that it is a line from the transmitter The Wires of this*l IOC) and that the receiver s is included in the outgoing circuiti' and that the circuit d pel'- forms no other work than to cause variations of pressure in the microphone.

Vhat I claim, and desire to secure b`y Letters Patent, isy l. In the art o f telephony the method of reinforcing the eiect of the main-line current upoii microphone-contacts by causing variations of current in a local circuit which influences the main-line magnet independently of the main line, to correspond with the variations of currentJ in the main line.

2. In the art of telephony, the method of reinforcing the eiect of the main-line current upon microphone-contacts by causing pulsations from a local battery, similar'in kind to the pulsations of the main line, to influence the main-line magnet independently of the main line.

8. In the art of telephony the method of reinforcing the effect of the main-line current upon microphone-contacts by causing pulsations from the main-line circuit to produce pulsations of the same kind in a local circuit which influences the lnain-line magnet independently of the main line, substantially as described.

4. In the art of telephony the method of reinforcing the eect of the main-line current upon microphone-contacts by causing electrical pulsations of higher potential but of the same form as the pulsations of the main line, to influence the main-line magnet independently of the main line.

5. In the art of telephony the herein-described method of reinforcing the eiiect of the main-line current by causing variations of pressure in a microphone produced by the main-line current, to produce in a local cir- `cuit which influences the main-line magnet independently of the main line; pulsations of the same kind as the pulsations of tlie main line, but f higher potential.

6. In the art of telephony the herein-described method which consists in causing variations of pressure ina microphone produced by the main-line current, to produce in a local circuit which influences the main-line magnet independently of the mainline, pulsations of a similar character to those of the mainline, and-causing the increased variations of pressure so produced in said microphone to influence an outgoing circuit which includes the receiver.

7. In the art of telephony the herein-described method which consist in causing va riations of pressure in a microphone produced by the main-line current, to produce in a separate and independent. circuit connected to the prim ary of an induction-coil the secondary of which coil influences the main-line magnet, pulsations of a similar character to those of the main line, and causing the increased Variations of pressure so produced in said microphone to influence an independent outgoing circuit which includes the receiver.

In testimony whereof I have signed my name to this specification in the presence of two subscribing witnesses.

GEORGE A. CARDVVELL. lVitnesses:

GEO. E. CRUsE, CHARLES S. JONES. 

